Stroke is a devastating disorder that leads to neuronal death and neurologic disability. We have shown that the brain's inherent ability to form new neuronal connections and restore lost function after stroke can be enhanced by neutralizing the inhibitory nature of the adult CNS through antibody therapy that neutralizes the protein Nogo-A. We now plan to study the ability of anti-Nogo-A immunotherapy to enhance functional recovery and neuronal plasticity in the chronic stroke impaired rat. This is an exciting and novel area of research and may benefit many more patients who suffer with chronic neurologic disabilities, even those resulting from causes other than stroke. In addition, understanding changes in neuronal plasticity following anti-Nogo-A immunotherapy given at a chronic stage of stroke could lead to improved therapeutic approaches for future clinical use. Therefore, we hypothesize that anti-Nogo-A immunotherapy when given to chronic stroke-impaired aged rats will result in improved functional outcome and enhanced anatomical plasticity in brain regions important for recovery. We will test our hypothesis in the following specific aims: Specific Aim #1- Determine whether treatment with anti-Nogo-A immunotherapy results in behavioral recovery when given two months after ischemic stroke in the aged rat. We will use behavioral tests of sensorimotor and cognitive recovery in the aged animal and study long term outcomes in order to enhance the translation of these results to clinical use. Specific Aim #2- Determine whether treatment with anti-Nogo-A immunotherapy results in neuroanatomical plasticity when given two months after ischemic stroke in the aged rat. This aim will employ neuroanatomical tract tracing and Golgi-Cox staining to examine axonal and dendritic plasticity in areas important for sensorimotor recovery. Specific Aim #3- Determine if movements in the stroke-impaired forelimb return to pre-stroke movement patterns or if other compensatory strategies occur after stroke and anti-Nogo-A immunotherapy in aged rats using kinematic analysis. The goals of the present proposal are to test if our novel immunotherapy improves functional recovery in the chronic stroke-impaired aged rat. The results of these studies will have a tremendous impact on the field of neurorehabilitation by changing the way we view chronic stroke, i.e. no longer will a deficit be thought of as stable or fixed, and recovery will be possible even for the chronically impaired stroke victim.